But arguably (I'm playing devil's advocate here!), why is this an issue? Let me put it this way:
Pre September 11th, ID was never requested for domestic flights. So arguably, I could have bought a ticket, decided not to travel and let Mr. X be YOWkid... He would have to go through security anyway.
So today, ie. post September 11th, we both carry a document to get past security, I get the boarding pass issued post security and give it to him to fly. We have both been scanned.
What difference does it really make? Yes, it's illegal, but not unsafe, if you know what I mean...